SHIGA TOXIN-PRODUCING ESCHERICHIA-COLI STRAINS FROM BOVINES - ASSOCIATION OF ADHESION WITH CARRIAGE OF EAE AND OTHER GENES

Out of 174 bovine Shiga toxin-producing Escherichia coli (STEC) strain s isolated from diarrheic calves in Germany and Belgium, 122 strains ( 70.1%) were selected because of their reactivity with the eae (E. call attaching and effacing gene) probe ECW1-ECW2. One hundred seven of th ese eae-positive strains (87.7%) harbored stx1 genes, 13 strains (10.7 %) had stx2 genes, and 2 strains (1.6%) had both stx genes. The strain s displayed 17 different O types, the majority (97 strains [79.5%]) be longing to O5 (5 strains), O26 (21 strains), O111 (13 strains) O118 (3 6 strains), O145 (9 strains), and O157 (13 strains). In the HEp-2 cell adhesion assay, 99 strains (81.1%) showed a localized adhesion, and 8 0 strains (65.6%) stimulated actin accumulation, as determined in the fluorescence actin staining test. None of the strains harbored genes c oding for bundle-forming pili (bfpA), clearly differentiating them fro m enteropathogenic E. coli. espB gene sequences were only detectable i n 23 (18.9%) of the ene-positive bovine STEC strains. Three different PCRs were established, differentiating between eae sequences of entero pathogenic E. coli strain E2348/69 (O127:H6) and STEC strain EDL933 (O 157: H7). Primers matching in the more heterologous downstream eae seq uences gave amplicons in only 8 of the 17 O types (O84:H-, O103:H2, O1 11:H-, O111:H2, O119:H25, O128:H-, O145:H28, and O157:H-). Only 15 STE C strains, belonging to serotypes O111:H-, O111:H2, O145:H28, and O157 :H-, gave amplicons in all three eae-specific PCRs. These data demonst rate that bovine STEC strains are a heterogeneous group of pathogenic bacteria, a lot of which share virulence markers with STEC strains cau sing infections in humans. However, in contrast to human STEC strains, bovine eae-positive STEC strains are mainly restricted to the stx1 ge notype. The observation that espB sequences are not highly conserved m ight have consequences for the serological recognition of the ESPB pro tein in patients. Like in human STEC strains, eae-related sequences ar e closely associated with certain E. coli O groups; however, they are not serotype specific.